Control apparatus



6 P. GIUFFRIDA CONTROL APPARATUS Filed Sept. 4, 1964 United States Patent 3,263,730 CONTROL APPARATUS Philip Giutfrida, North Andover, Mass, assignor to Electrohics Corporation of America, Cambridge, Mass, a corporation of Massachusetts Filed Sept. 4, 1964, Ser. No. 394,471

6 Claims. (Cl. 158-28) This invention relates to improved control apparatus and more particularly to control apparatus particularly adapted for incorporation in condition responsive systems of the type useful in supervising fuel burning apparatus and to such condition responsive systems. In condition responsive systems of the type employed for the supervision of flame established in the combustion chamber, it is desirable that the supervising system react very quickly to the presence or absence of flame so that the fuel valve may be closed promptly and thus prevent excessive amounts of unburned fuel from accumulating in the combustion chamber in the absence of flame. Flame sensing systems which have the desired rapid response to the presence or absence of flame are well known, but such systems are susceptible to component malfunction and may cause a flame detection system to falsely indicate the presence of flame. Should such a malfunction occur in a system supervising flame in a combustion chamber, an unsafe condition might arise, as the system, in the event of flame failure, would continue to react as if flame was present and permit the continued introduction of raw fuel into the furnace chamber. The accumulated raw fuel could be ignited explosively, either by the hot refractory or upon an attempt to re-ignite the burner, for example, with disastrous results.

Industry standards, therefore, state that an approved combustion control system must operate with a maximum time delay of four seconds between flame failure and shutdown of the fuel flow to the supervised combustion chamber. Component checking arrangements which check the operability of the system by simulating flame failure, therefore, must complete their cycle through flame relay dropout and flame relay pick-up Within that four second interval.

It is an object of this invention to provide a novel and improved combustion supervision system particularly adapted for use in supervising the existence of flame in a combustion chamber.

Another object of the invention is to provide a novel and improved component particularly adapted for incorporation in a self-checking type of combustion supervision system.

In accordance with the invention there is provided a condition sensor which produces an output signal in response to the sensing of a pre-established condition, which output signal is applied through suitable signal modifying circuitry (such as amplifiers) for the operation of an output device. In this invention the output device is a transient relay which, upon energization, closes a controlled circuit and then opens the circuit independently of the continued application of the energizing circuit to its input. The output circuits controlled by this device include a load device (fuel valve solenoid, for example) and also a flame absence simulator (a shutter, for example). Thus, when the output device is energized, energy is applied to both the load device and the flame absence simulator. Through coordination of the release times of these two devices, the load device may remain in held-in condition while the shutter drops out after interrupting the view of the sensor to the flame. With the shutter dropout, a signal is again applied through the modifying circuitry to energize the output device and repeat the cycle. Should the shutter fail to operate, for example,

3,263,730 Patented August 2, 1966 this transient cycle will not result and the load relay will not be re-energized so that it will drop out within its time delay.

The preferred form of the transient relay includes a chamber which holds a pool of mercury in the base portion of the chamber and a set of electrical contacts in the upper part of the chamber. A plunger is supported in the chamber above the pool of mercury but spaced from the electrical contacts disposed closely thereabove. The plunger has an orifice in it and means are provided to move the plunger rapidly downwardly through the mercury pool with the result that a jet of mercury is projected upwardly through the orifice which bridges the electrical contacts within the chamber, temporarily com pleting an electrical circuit. This circuit is completed only temporarily, however, as the level of the mercury under stable conditions, even with the plunger completely submerged in the pool, is below the level of the electrical contacts, and. hence, under those circumstances no electrical circuit is completed. In other words, an elec' trical circuit or ciruits is completed only upon the initial operation of the plunger moving downwardly.

With this transient relay, the combustion supervision system is periodically recycled in a simple, automatic manner, each time in response to the sensing of flame, and the simulation of flame absence is terminated promptly so that another indication of the presence of flame may re-energize the transient relay. If the condition to be sensed is not detected at regular intervals, the system is shut down in safe condition through the de-energization and dropout of the load device.

Other objects, features and advantages of the invention Will be seen as the following description of the preferred embodiment thereof progresses, in conjunction with the drawings, in which:

FIG. 1 is a schematic diagram of electrical control circuitry used in the invention;

FIG. 2 is a side view of the mercury impulse relay employed in the circuitry of FIG. 1; and

FIG. 3 is a sectional view of the relay shown in FIG. 2 taken along the line 3-3 of FIG. 2.

The combustion supervision system as shown in FIG. 1 supervises flame 10 in a combustion chamber which is supplied by fuel flowing through nozzle: 12 as con trolled by solenoid operated valve 14. A flame sensor 16, which may be of the avalanche discharge type, is con nected to view the flame 1d and is connected in the secondary circuit of an autotransformer 18 in series with a current limiting resistor 20. The autotransformer 18 is energized from a conventional power frequency source connected at terminals 22 and, upon avalanche breakdown, sensor 16 produces a transition which is reflected in the primary circuit and applied through inductors 24 and rectifier circuit 26 to an integrating circuit consisting of variable resistor 30, resistor 32 and capacitors 34 and 36.

The output of the integrating circuit is applied through diode 38 and resistor 40 for application to the control electrode 42 of a silicon control rectifier 44. A conventional biasing network including resistor 46, capacitor 48, and diode is connected between the cathode and control electrode of rectifier 44.

This rectifier operates as a pro-amplifier, and its output is applied to a second amplifier stage of similar configuration which includes rectifier 60. The output of the rectifier is applied through a transient relay coil across which is connected diode 72. This transient relay has a chamber 74 to which three electrodes 76, 78, and are connected. Electrode 76 is energized through a rectifier 82 and smoothing network comprising of resistor 84 and capacitor 86. Electrode 78 is connected to a solenoid 90 (having capacitor 92 connected across it) which operates a'shutter 94, while electrode 89 is connected to a load relay solenoid coil 96 (shunted by capacitor 98) which operates contacts 100. Contacts 100 are connected in circuit with an energy source 102 to operate fuel valve 14. A switch 104 (shown diagrammatically as a manually operable switch but which may be responsive to other types of inputs such as a flame initiation programming control, for example) is provided to initiate the flow of fuel to the combustion chamber.

Further details of the transient relay will be seen with reference to FIGS. 2 and 3. That relay includes a chamber 110 of reduced diameter in its base 112 which holds a pool of mercury 114. The upper portion of the chamber 110 is of larger diameter, and secured within that portion is a cap 116 of insulating material through which three electrodes 76, 78, 80 extend and are secured therein in spaced insulated relation. Each electrode has a loop 118 formed on the base of it. Also supported from the enclosing cap are a pair of stop structures 120. Interposed between the upper and lower portions of the chamber 110 is a plunger 122 which has an orifice 124 centrally located therein with a gradually tapered inlet 126 and a more rapidly tapered outlet passage 128. Spring 130 biases the plunger 122 upwardly against stops 120.

In operation, when the solenoid coil '70 is energized, the plunger is rapidly pulled down into the pool of mercury against the biasing force of spring 130 and a jet of mercury is forced up through the orifice 124 to bridge the loop terminal portions 118 of electrodes 76, 78, and 8t). This jet of mercury is forced up with considerable force and so bridges the electrodes for a significant period of time. However, the system is dimensioned so that the mercury level, with the plunger submerged in it, is below the lower edges of stops 120 so that no mercury in this condition can bridge the electrodes 76, 7 8, and 80. Thus, the circuit will be closed only for a transient period and will not be reclosed until the solenoid 70 has been deenergized and then re-energized after the plunger has risen out of the pool of mercury.

With respect to the operation of the circuitry of FIG. 1 incorporating this relay, initially the sensor 16 can see the flame in chamber when it first appears. The resulting flame presence signals are coupled through inductors 24 and the integrating circuitry after a suitable time delay operates the amplifiers 44 and to provide an energizing signal for relay 70. When that relay is energized, the jet of mercury rises, bridging the electrodes 76, 78, and and connecting input electrode 76 to electrodes 78, 80 to energize the solenoids and 96. The energization of solenoid 90 moves the shutter 94 into position between the flame and sensor 16 so that the sensor can no longer see flame and its output signal terminates. The capacitor 92 is a small capacitor proportioned to permit solenoid 90 to release within less than one second. Capacitor 98 connected across solenoid 96, however, is a larger capacitor and will hold that solenoid energized for a period of at least three seconds. Thus, when the transient relay 70 is energized, energy is applied to shutter solenoid and the load solenoid which will hold the shutter solenoid in flame absence condition for a period of less than one second, while the load relay will be held in for about three seconds. When no flame is sensed by sensor 16, solenoid 70 will be de-energized and allow the plunger 122 to rise again in a resetting operation. At approximately the same time, the sensor again sees flame and after the time delay in the signal modifying circuitry, the circuit will operate within the time delay period of the load relay so that that load will remain energized if the circuit is operating properly.

However, if the shutter should stick or the sensor continue to indicate the presence of flame in the absence of actual flame being sensed by it, for example, or for other reasons so that a signal continues to be applied to the solenoid 70 of the transient relay, the plunger will be held down in the pool of mercury and not be reset. As no replenishing charge is applied to the load relay and its capacitor 98 within the designed delay interval, the load relay 96 will drop out, opening contacts and deenergizing the solenoid of the fuel control valve so that the flow of fuel into the combustion chamber terminates and the flame 14 is extinguished in a safe condition.

While a preferred embodiment of the invention has been shown and described, various modifications thereof will be obvious to those skilled in the art, and, therefore, it is not intended that the invention be limited to the disclosed embodiment or to details thereof, and departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. Condition responsive control apparatus comprising condition sensing means which produces an output signal in response to the sensing of the existence of a predetermined condition,

transient relay means having an input circuit and an output circuit closed upon an initial energization of said input circuit,

said transient relay means opening said output circuit a predetermined period after the application of an energizing signal to said input circuit independently of the continued application of said energizing signal to said input circuit,

a load and a condition absence simulator connected to said output circuit, said load and said simulator each including means for providing a cycle time of activation following deenergization of said output circuit,

said condition absence simulator having a cycle time that is a fraction of the cycle time of said load, and

means to apply said sensing means output signals to the input circuit of said transient relay means such that said load and said condition absence simulator are energized simultaneously in response to the application of a signal to the input circuit of said transient relay means.

2. The apparatus as claimed in claim 1 wherein said transient relay means includes a chamber having a pool of mercury in the base of it,

a plunger disposed above said pool of mercury, having an orifice therein;

a pair of electrodes connected to said output circuit, said pair of electrodes being disposed within said chamber above said plunger in spaced relation therefrom, and

means connected to said input circuit to move said plunger downwardly through said pool of mercury in response to the application of a signal to said input circuit to force a jet of mercury upwardly through said orifice, which jet of mercury bridges said electrode elements to complete an electrical circuit therebetween.

3. The apparatus as claimed in claim 2 wherein said orifice is defined by a passageway having a tapered entrance of gradually decreasing cross section and a tapered exit passageway of increasing cross section.

4. The apparatus as claimed in claim 2 wherein said plunger moving means includes an electromagnetic element disposed adjacent the chamber for moving said plunger through said pool of mercury.

5. The apparatus as claimed in claim 2 and further including plunger positioning means located immediately below said electrode, resilient means biasing said plunger in a raised position out of said pool of mercury and in engagement with said plunger positioning means,

and wherein said plunger moving means includes an electromagnetic element disposed adjacent said chamber for moving said plunger away from said positioning means and downwardly into said pool of mercury.

6. Burner control apparatus for use with a fuel burner comprising flame sensing means which produces an output signal in response to sensed flame,

said flame sensing means adapted to be disposed to sense flame produced by said fuel burner in a combustion chamber and generate output signals as a function thereof,

a transient relay means having an input circuit and an output circuit closed upon an initial energization of said input circuit,

transient relay means opening said output circuit a predetermined period after the application of an energizing signal to said input circuit independently of the continued application of said energizing signal to said input circuit,

a fuel valve control relay and a flame absence simulator connected to said output circuit, means for providing a cycle time of activation for said fuel valve control relay following deenergization of said output circuit, means for providing a cycle time of activation for said flame absence simulator following deenergization of said output circuit,

References Cited by the Examiner UNITED STATES PATENTS 1,010,620 12/1911 Crumpton 200-412 2,798,213 5/1957 ROWell 340-213 3,143,162 8/1964 Graves et a1. 15828 3,190,341 6/1965 Giuffrida et al. 15828 20 JAMES W. WESTHAVER, Primary Examiner. 

1. CONDITION RESPONSIVE CONTROL APPARATUS COMPRISING CONDITION SENSING MEANS WHICH PRODUCES AN OUTPUT SIGNAL IN RESPONSE TO THE SENSING OF THE EXISTENCE OF A PREDETERMINED CONDITION, TRANSIENT RELAY MEANS HAVING AN INPUT CIRCUIT AND AN OUTPUT CIRCUIT CLOSED UPON AN INITIAL ENERGIZATION OF SAID INPUT CIRCUIT, SAID TRANSIENT RELAY MEANS OPENING SAID OUTPUT CIRCUIT A PREDETERMINED PERIOD AFTER THE APPLICATION OF AN ENERGIZING SIGNAL TO SAID INPUT CIRCUIT INDEPENDENTLY OF THE CONTINUED APPLICATION OF SAID ENERGIZING SIGNAL TO SAID INPUT CIRCUIT, A LOAD AND A CONDITION ABSENCE SIMULATOR CONNECTED TO SAID OUTPUT CIRCUIT, SAID LOAD AND SAID SIMULATOR EACH INCLUDING MEANS FOR PROVIDING A CYCLE TIME OF ACTIVATION FOLLOWING DEENERGIZATION OF SAID OUTPUT CIRCUIT, SAID CONDITION ABSENCE SIMULATOR HAVING A CYCLE TIME THAT IS A FRACTION OF THE CYCLE TIME OF SAID LOAD, AND MEANS TO APPLY SAID SENSING MEANS OUTPUT SIGNALS TO THE INPUT CIRCUIT OF SAID TRANSIENT RELAY MEANS SUCH THAT SAID LOAD AND SAID CONDITION ABSENCE SIMULATOR ARE ENERGIZED SIMULTANEOUSLY IN RESPONSE TO THE APPLICATION OF A SIGNAL TO THE INPUT CIRCUIT OF SAID TRANSIENT RELAY MEANS. 